Lower-Extremity Kinematics Differed Between a Controlled Drop-Jump and Volleyball-Takeoffs

Previous studies utilizing jump-landing biomechanics to predict anterior cruciate ligament injuries have shown inconsistent findings. The purpose of this study was to quantify the differences and correlations in jump-landing kinematics between a drop-jump, a controlled volleyball-takeoff, and a simulated-game volleyball-takeoff. Seventeen female volleyball players performed these 3 tasks on a volleyball court, while 3-dimensional kinematic data were collected by 3 calibrated camcorders. Participants demonstrated significantly increased jump height, shorter stance time, increased time differences in initial contact between 2 feet, increased knee and hip flexion at initial contact and decreased peak knee and hip flexion for both left and right legs, and decreased knee–ankle distance ratio at the lowest height of midhip for the 2 volleyball-takeoffs compared with the drop-jump ( P < .05, Cohen’s d z ≥ 0.8). Significant correlations were observed for all variables between the 2 volleyball-takeoffs ( P < .05, ρ ≥ .6) but were not observed for most variables between the drop-jump and 2 volleyball-takeoffs. Controlled drop-jump kinematics may not represent jump-landing kinematics exhibited during volleyball competition. Jump-landing mechanics during sports-specific tasks may better represent those exhibited during sports competition and their associated risk of anterior cruciate ligament injury compared with the drop-jump.